Resistance of Brahman and Hereford cattle to African ticks with reference to serum gamma globulin levels and blood composition.

Field collections of ticks from two breeds of cattle showed that the common species of ticks were Amblyomma hebraeum, Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi. The density of these species was higher on Hereford than on Brahman cattle. The results also indicated that the density of immature stages of the above-mentioned ticks is higher on Hereford than on Brahman cattle. A positive correlation was found between the number of ticks on the cattle and the serum gamma globulin levels, an indication of an increase in the production of antibodies. An inverse relationship was found between tick burden and red blood cell count and hemoglobin concentration. Other blood components, such as basophils, eosinophils and lymphocytes were not affected by the changes in the density of the tick populations. It appears that resistance may have been acquired by the hosts and that Brahman cattle may acquire resistance to a higher degree than Herefords.